Bump actions/checkout from 3 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/build.yml

@@ -8,21 +8,21 @@ jobs:
       - uses: dtolnay/rust-toolchain@stable
         with:
           components: rustfmt
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - run: cargo fmt --all -- --check
   clippy:
     runs-on: ubuntu-20.04
     steps:
       - uses: dtolnay/rust-toolchain@stable
         with:
           components: clippy
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - run: cargo clippy --all-features --all-targets
   rustdoc:
     runs-on: ubuntu-20.04
     steps:
       - uses: dtolnay/rust-toolchain@stable
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - run: cargo doc --all-features
   build:
     name: "Build and test"
@@ -43,7 +43,7 @@ jobs:
             rust: stable
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Install ${{ matrix.rust }} toolchain
         uses: dtolnay/rust-toolchain@master